Sources of error
Collection
Input
Storage
Manipulation
Output
Use of results
The main sources of error encountered in a GIS are
from:
- Errors are inherent in the
source materials
- Errors come from field data
collection
- Errors in the analysis of remotely sensed data
- Inaccuracies come from the
data input devices used eg digitising errors
- Inaccuracies are also inherent in the features
being mapped such as boundaries are often not clear cut
- Insufficient numerical precision
- Insufficient spatial precision
- Error is propagated as multiple overlay operations
are conducted
- Errors arise from the representation of boundaries
- the more convoluted the boundary the more scope for inaccuracies associated
with mismatching when overlays are performed
- Inaccuracy is inherent in the way that classes
are defined - many continuous features such as vegetation are mapped
as homogeneous with sharp boundaries when really they grade into one
another
- Choice of analysis model
- Misuse of logic
- Error propagation
- Error can be introduced at the plotting phase
- Error caused by inaccuracy of the output device
- Error caused by instability of the paper or
other medium on which output is printed
- Scaling inaccuracies
- Error is introduced when reports generated
by a GIS are inappropriately or incorrectly used
- Information can be incorrectly understood or misinterpreted
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Finding the error source
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Classify each of the following errors according
to the sources identified above. |
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